Dental implant and method for installing the same

ABSTRACT

A dental implant having an external thread configuration and/or a structure which facilitates a single step dental implant/prosthesis installation or which significantly reduces healing time between surgeries. The invention also relates to a method for installing such a dental implant.

[0001] This is a continuation-in-part of U.S. application Ser. No.09/175,007, filed Oct. 19, 1998.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention The present invention relates generallyto a dental implant, and more particularly to a dental implant with athread design and structure which provides for dramatically improvedloading to thereby facilitate an immediate load implant or an implantwith dramatically reduced healing time. The present invention alsorelates to a method of installing the above identified implant.

[0003] 2. Description of the Prior Art

[0004] Dental implants of various configurations currently exist in theart. These implants are installed into prepared bone sites and functionas a device for anchoring a component such as a tooth or dentalappliance in the patient's mouth. Examples of currently available dentalimplants are shown in U.S. Pat. No. 5,062,800 issued to Niznick, U.S.Pat. No. 5,368,160 issued to Leuschen, et al. and U.S. Pat. No.5,582,299 issued to Laxnaru. Existing dental implant devices commonlyinclude an implant having external threads for installation into aprepared bone site and a hollow interior with internal threads extendingfrom its superior or top end downwardly into the interior of the mainbody of the implant. Such internal threads are used for connecting animplant mount during the installation process and for connecting ahealing cap or a replacement tooth or other prosthesis when theinstallation is complete. During installation, the implant mount isconnected with the implant via a threaded clamp screw. The implant mountinterfaces with the implant through a hex connection which enables theimplant to be rotated via rotation of the implant mount. It is commonfor the implant to be provided to the attending surgeon in a pre-mountedposition with the implant mount connected to the implant by the clampscrew.

[0005] Installation of a dental implant in accordance with currentprocedures can be summarized as follows. After preparation of the bonesite, a dental hand piece with a placement adaptor is positioned ontothe implant mount via a hex or other connection. The implant is thenpositioned in the prepared bone site and installed by rotation of theimplant mount, and thus the implant, in a forward or clockwisedirection. The hand piece with attached placement adaptor is thenremoved from the implant mount and an open end wrench or other tool ispositioned onto the hex end of the implant mount to remove the same.Because the interface between the threads of a conventional implant andthe surrounding bone or tooth tissue is insufficient to resist thecompressive forces resulting from normal chewing or biting action, it isnecessary to allow the bone or tooth tissue in contact with such threadsto heal before a replacement tooth or other prosthesis can be applied.In most cases, this period can be six months or more. Thus, followinginstallation of a conventional implant and removal of the implant mount,a protective cover or healing screw is screwed into the internal threadsof the hollow interior for the duration of the required healing time. Insome cases the soft tissue surrounding the implant is extended andsutured over the healing screw, while in other cases the top of theimplant is substantially flush with the surrounding tissue and thehealing screw remains exposed during the healing period.

[0006] After the healing period has passed, the surgeon removes theprotective screw and installs a healing cap. This healing cap isnonfunctional and remains in place while the tissue heals, generally 4-6weeks. After this time period, the restoring doctor installs thereplacement tooth or other prosthesis. The replacement tooth or otherprosthesis commonly includes a mounting stem with external threads to bereceived by the internal threads of the hollow interior. Severaldrawbacks exist with respect to the current procedure. The primarydrawback is that current procedures require two surgeries at intervalsspaced by the required healing time: one surgery to install the implant,and a second surgery to remove the healing screw and install the healingcap and then later, the replacement tooth or prosthesis. The requiredhealing time can be up to six months or longer. With conventionalimplants, the six month or more waiting time is needed because theexternal threads of the implant do not efficiently distribute the loadand the bone is not strong enough immediately after installation to befully loaded or to support the implant with a connected replacementtooth or other prosthesis. Thus, with current implants embodying currentexternal designs, a healing period of up to six months or more isrequired after the first surgery (installation of the implant) to allowthe tooth bone to grow around the implant and to heal.

[0007] Prior implant designs have existed that allowed a tooth to beplaced on the implant immediately. However, these designs utilizedosseointegration rather than the current bone implant connection. Afurther design utilized a threaded implant in combination with a seriesof tapping instruments to obtain the required compressive forceresistance for immediately loading the tooth. Neither of these designs,however, has been widely accepted.

[0008] Accordingly, there is a need in the art for an improved dentalimplant with an improved thread configuration and an improved implantstructure which eliminates the second surgery or dramatically reducesthe time interval between the first surgery and placement of the finalprosthesis.

SUMMARY OF THE INVENTION

[0009] In contrast to the prior art, the present invention relates to adental implant which facilitates elimination of the second surgery toremove the healing cap and apply the prosthesis or which facilitatessignificant reduction of the time necessary between the first surgeryand placement of the final prosthesis. More specifically, the presentinvention relates to a dental implant structure in which the ratio ofthe minor to major thread diameters (the core to thread ratio) isdecreased, or the ratio of the major to minor thread diameters (thethread to core ratio) is increased. Specifically, these ratios aredecreased and increased, respectively, to increase the thread strengthof the implant to the point where healing time is eliminated orsubstantially reduced, thereby facilitating immediate or reduced timeloading. The present invention further relates to a dental implant withan improved external thread design which dramatically improves theresistance of the implant to chewing or compressive forces, and thussimilarly eliminates or substantially reduces the time period betweenimplant installation and the loading of the implant. Still further, theimplant of the present invention is designed to go into, but preferablynot through, the cortical plate. Accordingly, the length of the implantsof the present invention is preferably less than 20 mm, more preferablyno longer than about 15 mm and most preferably about 10-15 mm in length.

[0010] To accommodate immediate loading of the implant of the presentinvention, the two piece abutment and cap screw of prior art implantsare eliminated. Accordingly, in the present invention, the implant isprovided with a unitary implant in which the threaded portion and thebase or abutment portion for supporting the replacement tooth is asingle piece structure in which such portions are integrally joined withone another.

[0011] One embodiment of the implant of the present invention is toeliminate the hollow interior of the implant and to significantly reducethe core to thread ratio below the standard 0.75. To accommodate theeliminated interior an outwardly extending top or prosthesis receivingpost is provided above the neck of the implant to receive thereplacement tooth or other prosthesis. It has been found that thereduction in the core to thread ratio results in an unexpectedlyincreased resistance to compressive forces such as chewing or biting tothereby facilitate immediate loading of the implant.

[0012] A further embodiment of the present invention includes providingthe implant with an improved external thread design which includes firstand second helical threads which are interleaved with one another andwhich exhibit different outside or major diameters. Preferably at leastone of these helical threads is provided with a thread configuration inwhich the flat or the flatter thread side surface faces toward thedistal or non-head end of the implant.

[0013] A still further embodiment of the present invention is to providean implant less than 20 mm in length with the thread design describedabove.

[0014] Accordingly, an object of the present invention is to provide adental implant which can be fully installed, together with thereplacement tooth or other prosthesis, in a single surgery.

[0015] Another object of the present invention is to provide a dentalimplant which eliminates the hollow interior for attaching theprosthesis.

[0016] A further object of the present invention is to provide animmediate load dental implant to be installed into, but preferably notthrough, the cortical plate, thereby providing an implant of preferablyless than 20 mm.

[0017] A still further object of the present invention is to provide adental implant with a reduced core to thread ratio and morespecifically, a core to thread ratio of no greater than 0.70.

[0018] A still further object of the present invention is to provide,independently or in combination with an implant of reduced core tothread ratio and/or an implant with a length of less than 20 mm, aunitary implant having an integral threaded portion and tooth supportingportions.

[0019] A still further object of the present intention is to provide adental implant with an improved external thread configuration tofacilitate immediate loading to reduce the interval between first andsecond surgeries.

[0020] A still further object of the present invention is to provide adental implant structure by which the thread to core ratio can besignificantly increased to a ratio of 1.40 or greater.

[0021] These and other objects of the present invention will becomeapparent with reference to the drawings, the description of thepreferred embodiment and the appended claims.

DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a side view, partially in section, of a conventionaldental implant.

[0023]FIG. 2 is an elevational side view of a conventional healing screwfor use with the dental implant of FIG. 1.

[0024]FIG. 3 is an elevational side view of a replacement tooth for usewith the dental implant of FIG. 1.

[0025]FIG. 4 is a side view, partially in section, of one embodiment ofthe dental implant in accordance with the present invention.

[0026]FIG. 5 is an enlarged sectional view of the thread configurationof the implant of the embodiment shown in FIG. 4.

[0027]FIG. 6 is an elevational bottom view from the distal end of thedental implant of FIG. 4.

[0028]FIG. 7 is an elevational top view from the proximal or head end ofthe dental implant of FIG. 4.

[0029]FIG. 8 is a side view, partially in section, of a secondembodiment of the dental implant in accordance with the presentinvention.

[0030]FIG. 9 is an enlarged view of the thread configuration of theembodiment of the dental implant as shown in FIG. 8.

[0031]FIG. 10 is an elevational bottom view from the distal end of thedental implant of FIG. 8.

[0032]FIG. 11 is an elevational top view from the proximal or head endof the dental implant of FIG. 8.

[0033]FIG. 12 is a side view, partially in section, of a thirdembodiment similar to that of FIG. 8, but with a modified thread design.

[0034]FIG. 13 is a side view, partially in section, of a fourthembodiment of the dental implant of the present invention, which view issimilar to that of FIG. 8, but with a further modified thread design.

[0035]FIG. 14 is an enlarged view of the thread pattern of the dentalimplant embodiment of FIG. 13.

[0036]FIG. 15 is an elevational side view, partially in section, of areplacement tooth for use with the implants of FIGS. 8, 12 and 13.

[0037]FIG. 16 is a modified prosthesis receiving post for theembodiments of FIGS. 8, 12 and 13.

[0038]FIG. 17 is a modified replacement tooth for use with theprosthesis receiving post design of FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0039] The present invention relates to improvements in a dentalimplant. In general, a dental implant provides support for a replacementtooth or other prosthesis and thus is anchored into a tooth root, boneor other tissue. The dental implant provides support for suchreplacement tooth or prosthesis at its proximal or superior end. Adental implant does not function to secure two or more pieces of tissue,bones or other elements together as in conventional bone screws, nordoes it function to provide any significant resistance to pulling outforce as in conventional tissue or bone screws.

[0040] Reference is first made to FIGS. 1, 2, and 3 showing aconventional dental implant and related structures known in the art.Specifically, FIG. 1 illustrates a conventional dental implant 10 havinga main body portion 11, a proximal or superior end 12 and a distal orinferior end 14. The proximal end 12 is provided with a conventional hexconfiguration 15 to enable the implant to be rotated and installed intoa pre-drilled hole in a tooth root or bone. The dental implant of FIG. 1is provided with a hollow interior 16 which extends from the proximalend 12 into the main portion 11 of the implant for a substantialdistance toward the distal end 14. This hollow interior 16 is providedwith internal threads. The exterior of the implant 10 is provided withthreads 18 for securement to a tooth structure.

[0041] Conventional dental implants have a core to thread ratio greaterthan 0.70 with the standard being about 0.75 or greater. This translatesinto a thread to core ratio of less than about 1.40, with the standardbeing about 1.20 or less. The core to thread ratio is the ratio betweenthe dimension at the innermost edge of the thread (the minor diameter)to the dimension at the outermost edge of the thread, while the threadto core ratio is the ratio of the major diameter to the minor diameter.

[0042]FIGS. 2 and 3 illustrate elements designed for use with theconventional dental implant of FIG. 1. Specifically, FIG. 2 illustratesa healing screw 17 having a proximal or head end 20 and an elongatedstem portion 19 extending from the head 20 toward a distal end. The stemportion 19 is provided with external threads designed to be received bythe internal threads of the hollow interior 16 (FIG. 1) and issubstantially smaller in diameter than the proximal end 20. The healingcap 17 is conventionally screwed into the hollow interior 16 of theimplant 10 after installation of the implant and during the healingperiod for the surrounding bone or tooth tissue.

[0043]FIG. 3 illustrates a conventional replacement tooth 21 having anelongated externally threaded stem 22 at its distal end and areplacement tooth portion 24 at its proximal end. The external threadsof the stem 22 are designed to mate with the internal threads of theinterior portion 16. The replacement tooth 21 is installed into theimplant 10 of FIG. 1 after the necessary healing period has elapsed andthe healing cap 17 (FIG. 2) has been removed.

[0044] General reference is next made to FIGS. 4-7 showing a firstembodiment of a dental implant 25 in accordance with the presentinvention. The dental implant 25 includes a main body portion 26 with aproximal or superior end 28 and a distal or inferior end 29. Asillustrated best in FIGS. 4 and 6, the distal end 29 is provided with aplurality of cutting edges 32 to provide the implant with self tappingcapabilities. The cutting edges 32 or other self-tapping structures asapplied to dental implants are well known in the art and such structuresare incorporated herein by reference. In the preferred embodiment, thedistal end 29 of the implant 25 is also provided with a through-hole 34for later bone growth, if desired. Such hole 34, however, is notnecessary to achieve the other benefits of the implant 25.

[0045] As shown in FIGS. 4 and 7, the proximal end 28 is provided with arotation head in the form of a hex end or portion 30 for engagement by ahand piece or other tool or adaptor for the purpose of rotating theimplant 25 during installation. A hollow interior 31 extends from theproximal end 28 into the main portion 26 of the implant 25 for asubstantial distance toward the distal end 29. The hollow interior 31 isprovided with internal threads to receive a conventional healing cap orreplacement tooth such as as shown in FIGS. 2 and 3, respectively, orany other prosthesis or attachment intended for use with dentalimplants. In this embodiment, the diameter of the hollow interior 31 isreduced relative to that of conventional implants to accommodate thereduced core to thread ratio.

[0046] The exterior of the main body of the implant 25 as shown in FIG.4 is provided with a plurality of external threads comprising a firstseries of helical threads 35 extending from the distal end 29substantially to the proximal end 28 and a second series of helicalthreads 36 interleaved between the first series of helical threads 35and also extending from the distal end 29 substantially to the proximalend 28. In the preferred embodiment, the helical threads 35 and 36 havefirst and second outer diametrical dimensions which are different fromone another. As shown generally in FIG. 4 and more specifically in FIG.5, the outer or major diameter of the first series of helical threads 35is greater than the outer or major diameter of the second series ofhelical threads 36.

[0047] With reference to FIG. 5, each of the first series of helicalthreads 35 includes an outer edge 38 extending helically around theimplant 25 and defining the thread diameter or major diameter of thethreads 35. The specific size of this outer or major diameter, which istwice the radius “R₀₁” shown in FIG. 5 as the distance between the edge38 and the implant centerline 33, will depend of the particular size ofthe implant. Conventional implants normally include implants withdiameters of 3 mm to 6 mm, with most standard implants being 4 mm or 5mm. Implants are conventionally provided in lengths from 10 mm to 15 mmand specifically in lengths of 10 mm, 11.5 mm, 13 mm and 15 mm.

[0048] The helical threads 35 also include an inner edge 39. The inneredge 39 defines the core diameter or minor diameter of the thread 35which, as shown in FIG. 5, is twice the distance “R_(i)” between theedge 39 and the centerline 33. The core diameter 39 defines theinnermost portion of the thread 35. Like the outer edge 38, the inneredge 39 of the thread extends helically around the implant 25. The coreto thread ratio or the minor to major diameter ratio of thread 35 isdetermined by comparing the minor diameter defined by twice the distance“R_(i)” to the major diameter defined by twice the distance “R₀₁”.Preferably this ratio R_(i)/R₀₁ is about 0.70 or less and morepreferably about 0.60 or less. The range of core to thread ratios forimplants in accordance with the present invention is preferably 0.40 to0.70, more preferably 0.45 to 0.65 and most preferably 0.50 to 0.60.These ratios are based on a major diameter of 4 mm and a minor diameterof about 2.25 mm for a 4 mm implant, and a major diameter of 5 mm and aminor diameter of about 3 mm for a 5 mm implant.

[0049] With these core to thread ratios, it has unexpectedly been foundthat the resistance of the implant to compressive forces is dramaticallyincreased. This increase is significantly greater than what one wouldexpect by comparing the relative thread surface areas of the implant ofthe present invention with those of conventional implants with astandard core to thread ratio of about 0.75.

[0050] In a preferred embodiment, the outer edge 38 terminates in a flatsurface generally parallel to the longitudinal axis of the implant asshown. Although it can, if desired, terminate substantially at a point,it is preferred that the outer edge 38 terminate in a flat portion asshown having a dimension “A₁” of less than about 0.2 mm and morepreferably between about 0.03 and 0.15 mm.

[0051] The particular height H₁ of the thread 35 defined by the distancebetween the outer edge 38 and the inner edge 39 will vary with theparticular size of the implant, the amount of torque desired to installthe implant and the compressive force resistance desired.

[0052] The thread 35 also includes a pair of side surfaces extendinghelically from the distal end 29 of the implant to the proximal end 28.These side surfaces include a distal or distal facing surface 40 and aproximal or proximal facing surface 41. As shown best in FIG. 5, thesesurfaces 40 and 41 form angles DA₁ and PA₁, respectively, with a lineextending perpendicular to the longitudinal or center axis 33 of theimplant. Although these two angles DA₁ and PA₁ can be the same, it ispreferred that the angle DA₁ be smaller than the angle PA₁ (or that theangle PA₁ be larger than the angle DA₁). More specifically, it ispreferred that the angle DA₁ be less than about 45°, more preferablyless than about 25°, and most preferably less than about 10°. Incontrast, it is preferred that the angle PA₁ be between about 45 and 5°,more preferably between about 40 and 10°, and most preferably betweenabout 35 and 20°. With this structure, it is preferred that the surface40, which comprises the flatter surface or smaller angle face the distalend of the implant as shown.

[0053] The thread design 36 is similar to that of the thread 35 exceptthat its outer or major diameter defined by twice the distance “R₀₂”between the outer edge 42 and the centerline 33 is less than the majordiameter of the thread 35. Similar to the thread 35, the inner dimensionof the thread 36 is defined by the inner edge 39. The core to threadratio, or minor to major diameter ratio, of the thread 36 is defined asthe ratio of its minor diameter (twice the distance “R_(i)”) to itsmajor diameter (twice the distance “R₀₂”). This core to thread ratio isexpected to be greater than the core to thread ratio of the thread 35since the denominator of the ratio is less. However, even this ratio ispreferably less than the standard ratio of about 0.75. It iscontemplated, however, that the core to thread ratio of the smallerthread in a thread pattern of multiple thread diameters 1 could begreater than the standard core to thread ratio of 0.75 without deviatingfrom the present invention.

[0054] In determining core to thread ratio in a multiple thread diameterpattern in accordance with the present invention, the major diameter ofthe largest thread is used. Thus, in the embodiment of FIGS. 4 and 8,the preferred values of the core to thread ratio as set forth above withrespect to the thread 35 (the largest thread) are applicable.

[0055] Similar to the thread 35, the outer edge 42 of the thread 36 isprovided with a flat portion extending helically around the implant.Although this outer portion 42 can terminate at a point, it preferablyterminates at a flat portion with a dimension A₂ of less than about 0.1mm and more preferably between about 0.3 and 0.1 mm

[0056] Also, similar to thread 35, the second helical thread 36 includesa pair of sides extending helically along the length of the implant.Specifically, these sides include a distal or distal facing side 44 anda proximal or proximal facing side 45. These sides 44 and 45 form anglesDA₂ and PA₂ with a line extending perpendicular to the longitudinal orcenter axis 33 of the implant, respectively. Although these angles canbe the same, it is preferred for the angle DA₂ of the distal side 44 tobe smaller than the angle PA₂ of the proximal side 45 (or the angle PA₂to be larger than the angle DA₂). Preferably the angle DA₂ of the distalside 44 is less than 45°, more preferably less than about 25° and mostpreferably less than about 10°. The angle PA₂ of the proximal side 45 ispreferably between about 45 and 5°, and more preferably between about 35and 10°.

[0057] The distance between the threads 35 and 36 measured from the topouter edge of the thread 35 to the top outer edge of the thread 36 isdefined by the distance W₁, while the distance between the threads 36and 35 measured from the top outer edge of the thread 36 to the topouter edge of the thread 35 is defined by the distance W₂. Thesedistances relate to the pitch of the threads or the number of threadsper unit length. Preferably, the distances W₁, and W₂ are such as toprovide a pitch for the threads 35 of about 8-20 threads per inch and asimilar pitch for the threads 36 of about 8-20 threads per inch. Morepreferably, the thread pitch should result in 10-18 threads per inch andmost preferably about 12 threads per inch. Although the pitch of thethreads 35 and 36 is preferably constant throughout the length of theimplant, the pitch can be designed to vary, if desired.

[0058] In the preferred embodiment, a 13 mm implant has about 4 to 10turns of the thread 35. More preferably, a 13 mm implant has about 6 to8 turns of the thread 35. This translates to a thread 35 density pitchof about 12 to 16 threads per inch.

[0059] Although the implant of the present invention can be of variouslengths, it is preferably of a length that will penetrate the corticalplate, but preferably not go through it. Thus, the preferred implantlength in accordance with the present invention is less than 20 mm. Morepreferably, the length is no greater than 15 mm, and most preferably thelength is about 10 to 15 mm. For purposes of the present invention, thelength of the implant is that portion comprised of the threads.

[0060] Reference is next made to FIGS. 8, 9, 10 and 11 illustrating asecond embodiment of a dental implant 47 of the present invention.Specifically, the embodiment of the FIG. 8 includes a main implantportion 46 having first and second helical threads 50 and 51,respectively, extending from the distal end 48 toward the proximal end49. The main body portion 46 and threads 50 and 51 of the embodiment ofFIG. 8 are substantially the same as that of the embodiment of FIG. 4.Accordingly, the elevational distal end view of FIG. 10 of theembodiment of FIG. 8 is substantially the same as the distal end view ofFIG. 6. The enlarged thread configuration illustrated in FIG. 9 is alsosimilar to that shown in FIG. 5 with respect to the embodiment of FIG.4. Specifically, the first and second helical threads 50 and 51 of theembodiment of FIG. 8 extend helically along a substantial length of theimplant and are interleaved between each other. Further, although notspecifically described, the core to thread ratios of the threads 50 and51 and their respective configurations and dimensions are similar tothose described and shown above with respect to FIG. 5. Further, each ofthe threads 50 and 51 include distal or distal facing sides 55 and 58,respectively, and proximal or proximal facing sides 56 and 59,respectively. The angles which these sides form with a line extendingperpendicular to the longitudinal axis or center line of the implant issimilar to that disclosed with reference to FIG. 5.

[0061] The embodiment of FIG. 8 differs from that of FIG. 4 in that anextended neck 43 is provided between the threaded portion and theproximal end 49, a head or prosthesis receiving post 52 is provided tothe proximal end 49 of the implant and the hollowed out interior portion31 of the embodiment of FIG. 4 is eliminated. Further, the proximal endof the head or post 52 is provided with a structure 54 for rotating theimplant 47 during installation. In the preferred embodiment, thisstructure 54 comprises a pair of flats on opposite sides of the post 52.The structure 54 is designed to mate with a hand piece or other tool oradaptor. However, this structure can be any structure which enables theimplant to be rotated. It is also contemplated that a portion of thehead or post 52 can be provided with a conventional hex end to receivean appropriate tool for rotation.

[0062] As shown best in FIG. 8, the head 52 includes a circumferentialgroove 53 near its upper end. This groove is intended to receive arubber loop to assist in installation of the implant. A plurality ofgrooves 57 are also provided for use when constructing impressions ortemporaries.

[0063] It is contemplated that with the embodiment of FIG. 8, areplacement tooth or other prosthesis such as that illustrated in FIG.15 would be connected to the post 52. As shown in FIG. 15, thereplacement tooth includes a conventional tooth exterior 60 and aninterior conforming substantially to the exterior figuration of the post52 and portion 54 of FIG. 8. It is contemplated that with the embodimentof FIG. 8, the replacement tooth of FIG. 15 would be secured to the post52 through an appropriate adhesive. The neck 43 can be of varyingheights depending on the nature of the tissue and the particularprosthesis used. Preferably, the height of the neck 43 is between about0.5 and 8 mm and most preferably between about 1 and 5 mm.

[0064] The embodiment shown in FIG. 12 is an embodiment similar to thatof FIG. 8 except that the threads 64 of the implant of FIG. 12 are ofthe same diameter and are symmetrical. The core to thread ratio of thethreads 64, however, are substantially the same as that of theembodiment of FIG. 4. Specifically, the core to thread ratios arepreferably 0.70 or less and more preferably 0.60 or less. The preferredranges of such ratios are 0.40 to 0.70, with more preferred and mostpreferred ratios being 0.45 to 0.65 and 0.50 to 0.60, respectively. FIG.12 also includes a modified prosthesis receiving post comprising thepost 63 extending outwardly from the neck 43 and a hexagonal end 54 tofacilitate rotation of the implant.

[0065] The embodiment of FIG. 13 is similar to that of the embodiment ofFIG. 12 in that the threads 66 are of equal outer diameter, but isdissimilar to that of FIG. 12 in that the threads are not symmetrical.The details of this thread configuration are shown in FIG. 14. As shownin FIG. 14, the distal or distal facing side 68 of the threads 66 formsan angle DA₃ with a line perpendicular to the longitudinal axis orcenter line 33 of the implant, while the proximal or proximal facingside 69 of the threads 66 forms an angle PA₃. In the embodiment of FIGS.13 and 14, the angle DA₃ is less than the angle PA₃ (or the angle PA₃ isgreater than the angle DA₃), with the preferred values of those anglesbeing similar to those described above with respect to FIG. 5.

[0066]FIG. 16 illustrates an alternate prosthesis receiving post for theimplant embodiments of FIGS. 8, 12 and 13. In the embodiment of FIG. 16,the head or post portion 52 is provided with an internal recess 70. Thisrecess 70 is provided with internal threads which are intended toreceive external threads from a replacement tooth such as thatillustrated in FIG. 17. In FIG. 17, the replacement tooth includes amain replacement tooth portion 71 and an elongated stem portion 72having external threads matching the internal threads of the internalportion 70 of FIG. 16. As shown, the stem portion 72 is positionedentirely within the tooth portion 71. To install the replacement toothof FIG. 17 on the implant of FIG. 16, the stem 72 is positioned into theinterior portion 70 and rotated until tight.

[0067] Having described the detailed structure of the preferredembodiment of the present invention, the use of the dental implant andthe method aspect of the present invention can be understood best asfollows: First, a dental implant is provided which includes a proximalend, a distal end and an externally threaded shaft. The shaft preferablyincludes a core to thread ratio as specified above. The shaft furtherincludes first and second helical threads which are interleaved with oneanother and embody first and second thread diameters, with one of thethread diameters being different than the other. The implant alsopreferably includes a prosthesis receiving post integrally positioned atthe proximal end of the implant and extending outwardly from theproximal end to receive a prosthesis. The method further includesdrilling or boring a hole into a tooth root or bone at a desiredlocation and then inserting the distal end of the implant into the holeand rotating the dental implant to a desired degree of installation.Preferably, the implant is not installed through the cortical plate.Finally, a replacement tooth or other prosthesis is mounted or attachedto the prosthesis receiving post either via a threaded connection,adhesives, or the like. This installation of the replacement tooth orprosthesis is preferably performed immediately. Thus, the preferredmethod is a single surgery method in which both the installation of theimplant and the installation of the prosthesis are completed in a singleoffice visit.

[0068] Although the description of the preferred embodiment has beenquite specific, it is contemplated that various modifications could bemade without deviating from the spirit of the present invention.Accordingly, it is intended that the scope of the present invention bedictated by the appended claims rather than by description of thepreferred embodiment.

1. A dental implant comprising: an elongated externally threaded shafthaving a longitudinal axis; a distal end; a proximal end; a rotationhead at said proximal end; and said threaded shaft including a pluralityof helical threads with the core to thread ratio of such threads beingabout 0.70 or less and said implant being less than 20 mm in length. 2.The dental implant of claim 1 wherein said core to thread ratio is about0.45 to 0.65.
 3. The dental implant of claim 2 wherein said core tothread ratio is about 0.50 to 0.60.
 4. The dental implant of claim 1wherein said threaded shaft includes first and second helical threadsinterleaved with one another and having different diameters.
 5. Thedental implant of claim 4 wherein said first thread includes a firstproximal facing surface facing said proximal end and a first distalsurface facing said distal end, wherein said first proximal facingsurface forms a first acute proximal angle relative to a lineperpendicular to said longitudinal axis, wherein said first distalfacing surface forms a first acute distal angle relative to a lineperpendicular to said longitudinal axis and wherein said first acuteproximal angle is greater than said first acute distal angle.
 6. Thedental implant of claim 5 wherein said first thread diameter is greaterthan said second thread diamter.
 7. The dental implant of claim 6wherein said first acute distal angle is less than 25°.
 8. The dentalimplant of claim 1 including a replacement tooth receiving portionextending from said proximal end and being integrally formed with saidthreaded shaft.
 9. The dental implant of claim 8 wherein said threadedshaft is free of any internal threaded portion.
 10. The dental implantof claim 1 including an internally threaded bore extending into saidshaft from said proximal end and along said longitudinal axis.
 11. Thedental implant of claim 4 wherein said first and second threads includesfirst and second proximal facing surfaces forming first and second acuteproximal angles, respectfully, relative to a line perpendicular to saidlongitudinal axis, wherein said first and second threads include firstand second distal facing surfaces forming first and second acute distalangles, respectfully, relative to a line perpendicular to saidlongitudinal axis, and wherein said first and second acute proximalangles are greater than their corresponding first and second acutedistal angles.
 12. The dental implant of claim 1 including an integraldental prosthesis receiving post positioned at said proximal end andextending outwardly therefrom.
 13. The dental implant of claim 12wherein said shaft is free of any internal bore.
 14. The dental implantof claim 1 in combination with a dental prosthesis.
 15. The dentalimplant of claim 1 being no greater than 15 mm.
 16. A method ofinstalling a dental implant and appliance comprising the steps of:providing a dental implant having a length less than 20 mm and aproximal end, a distal end and an externally threaded shaft, said shaftincluding a plurality of helical threads having a core to thread ratioof 0.70 or less and said implant further including a prosthesisreceiving post positioned at said proximal end and extending outwardlytherefrom; drilling a hole into a tooth root or bone at a desiredlocation; inserting said distal end into said hole and rotating saiddental implant to a desired degree of installation; and attaching aprosthesis to said prosthesis receiving post.
 17. The method of claim 16wherein said prosthesis is attached to said receiving post immediatelyafter said insertion step.
 18. A dental implant, comprising: anelongated externally threaded shaft having a longitudinal axis and acore to thread radio of no greater than 0.70; a distal end; a proximalend; and an integral prosthesis receiving post positioned at saidproximal end and extending outwardly therefrom.
 19. The dental implantof claim 18 wherein said plurality of threads include a proximal facingsurface forming a proximal angle with a line perpendicular to saidlongitudinal axis and a distal facing surface forming a distal anglewith a line perpendicular to said longitudinal axis and wherein saidproximal angle is greater than said distal angle.
 20. The dental implantof claim 18 being less than 20 mm in length.